module 2 - 5.3 diffusion and passive transport Flashcards
what does a passive process mean?
when something doesn’t require any EXTRA external energy
what is diffusion?
net movement of anything from a region of high to low concentration (down concentration gradient)
what is diffusion driven by?
a concentration gradient
what is a change in concentration over a distance called?
a concentration gradient
where does the energy for diffusion come from?
the kinetic energy of the particles
(does not need external energy)
what is brownian motion?
relies on the random movement of particles suspended in a liquid or gas
what is the entropic force?
no force moving molecules down concentration gradient
what is ficks law?
- higher temp, higher diffusion rate
- higher conc. difference, higher diffusion rate
- higher SA of exchange surface, higher diffusion rate
- higher membrane thickness, lower diffusion rate
what is equilibrium?
when a concentration gradient has equalised diffusion
what happens to the particles at equilibrium?
- they do NOT stop moving
- appears to be no directional movement as particles are all moving in the same direction
what is bulk flow?
the movement of a whole substance or all the particles in a direction
what happens to the air when the lungs are used as an example of diffusion?
- diffusion of oxygen molecules in air into blood due to concentration gradient
- oxygen particles moving within all other particles in the air
what happens to the air when the lungs are used as an example of bulk flow?
- bulk flow of air into alveoli due to a pressure gradient (high outside lungs, low inside) when breathing in
- bulk flow stops when pressure is equalised in alveoli
what type of transport and diffusion occurs between the phospholipids?
- passive transport
- diffusion/ simple diffusion
what type of transport and diffusion occurs through a transmembrane protein?
- passive transport
- facilitated diffusion
what happens to non-polar molecules during simple diffusion across across a membrane?
- small non-polar molecules can freely diffuse through cell membrane (O, CO2, H20 etc)
- bigger non-polar molecule, lower diffusion rate
- water can diffuse through cell membrane more slowly as partial charges being repelled by hydrophobic core of membrane
what happens to polar molecules during simple diffusion across across a membrane?
- ## large and polar diffuse through cell slowly or not at all e.g. glucose
what happens to fully charged molecules during simple diffusion across across a membrane?
cannot easily diffuse thorough cell membrane as charges are repelled by hydrophobic core
what is simple diffusion?
diffusion of substances through tails and phospholipid bilayer
which diffusion happens faster and why?
- facilitated diffusion
- happens through a transmembrane protein (direct route)
what is the pore in the protein made of in the phospholipid bilayer?
amino acids in a polypeptide chain
what happens during facilitated diffusion across a membrane?
- involves intrinsic/ transmembrane proteins
- protein allows diffusion across cell membrane of specific molecule through pore in protein (down conc. gradient)
which proteins are involved in facilitated diffusion?
- carrier proteins
- channel proteins
what does a channel protein do within facilitated diffusion?
- has a pore that can open or close, pore is specific to a molecule
- high rate of diffusion but is saturable due to limited pores available
what does a carrier protein do within facilitated diffusion?
- has a pore that’s never fully open across the membrane
- protein changes shape when specific molecule binds to it (causes conformational (shape) to change)
- low rate of diffusion due to limited pores available
why do carrier proteins change shape when a specific molecule binds to it?
allows molecule to cross cell membrane
where does the energy for the conformational (shape) to change?
the binding of the molecule
NOT ATP
what is dialysis tubing?
artificial semi-permeable membrane tubing
what is dialysis tubing used for?
teaching aid to demonstrate principles of diffusion, brownian motion, osmosis, and the movement molecules across restrictive membranes
